Two donkeys are standing $400 \, m$ apart. The first donkey can run at a speed of $3 \, m/s$ and the second can run at $2 \, m/s$. If both donkeys run towards each other, after how much time (in $seconds$) will they meet?

The speed of a train going from Nagpur to Allahabad is $100 \text{ km/h}$,while its speed is $150 \text{ km/h}$ when coming back from Allahabad to Nagpur. What is the average speed during the whole journey in $\text{km/h}$?

Two trains,$130 \,m$ and $110 \,m$ long,are moving in the same direction. The faster train takes $1 \,minute$ to pass the other completely. If they are moving in opposite directions,they pass each other completely in $3 \,seconds$. Find the speed of each train (in $m/s$).

Walking at the rate of $4 \, km/h$, a man covers a certain distance in $2 \, \text{hours} \, 45 \, \text{minutes}$. Running at a speed of $16.5 \, km/h$, the man will cover the same distance in how many minutes?

Two guns were fired from the same place at an interval of $13 \text{ minutes}$,but a person in a train approaching the place hears the second shot $12 \text{ minutes } 30 \text{ seconds}$ after the first. Find the speed of the train,assuming that sound travels at $330 \text{ m/s}$ (in $\text{km/hr}$).

$A$ man travelled a distance of $80\, km$ in $7\, hours$,partly on foot at the rate of $8\, km/h$ and partly on bicycle at $16\, km/h$. The distance travelled on foot is (in $km$):